This proposal will continue investigation of the patterns of interaction among speech articulators. We plan to use strain gauge transduction of lip and jaw movement, electromyography, and other measurement techniques to explore articulatory interactions under various experimental conditions in normal speakers and stutters. The approach is to describe movements and/or muscle activity patterns among articulators, to explore changes in patterns across articulators under various perturbing conditions, and to use these findings to derive hypotheses about principles of operation for the speech production systems. The specific studies proposed follow from previous work on this grant. The areas of investigation are to identify: 1) the proportionality of upper lip-lower lip interactions, 2) effects of viscous and inertial jaw loading on lip and jaw interactions, 3) bilateral interactions for both the lip and the jaw, 4) the effects of changing the speech content and timing of sensory (auditory) input on articulatory interactions (lip, jaw, and voicing), 5) the effects of changing the timing of nonspeech sensory (visual and auditory) information on interactions between lip and jaw movements, and 6) the effects of phase dependent sensory inputs on coordination and control of rhythmic activity in stutterers and nonstutterers. The scientific discipline involved is speech pathology. The experiments are designed to provide understanding of speech production processes that will serve as a scientific basis for future developments in diagnosis and therapy for speech disorders. Our approach takes advantage of insights about movement control developed in the disciplines of neurophysiology, motor physiology, zoology, and neurology.